Rod bolts, stretch or tourque?
Rod bolts, stretch or tourque? I have ARP rod bolts, the chrome 12 point ones. Is it better to torque them or measure for stretch? I have seen credible sources say both are acceptable. Not sure which I should go with.
TECH Apprentice
Joined: Aug 2004
Posts: 321
Likes: 0
From: Buffalo, N.Y.
Both are acceptable. Everything I've read on the subject, says that measuring bolt stretch is the most consistently accurate way to tighten a fastener. Tests have been done that measured the bolt stretch on HUNDREDS of bolts, AFTER they were torqued to the same reading using a certified torque wrench. The bolt stretch readings were all over the road. Where practical, it's really the only way to go. If there is no practical way to measure bolt stretch (headers, heads, etc.), use studs, instead.
I wouldn't think it would be disasterous to use a GOOD torque wrench while building your typical street engine. If you're building an engine to insane power levels, or are building Nextel Cup engines, or engines for the Indy 500, you might want to think about buying a bolt stretch gauge.
Measuring bolt stretch tells the truth, the whole truth, and nothing but the truth.
I wouldn't think it would be disasterous to use a GOOD torque wrench while building your typical street engine. If you're building an engine to insane power levels, or are building Nextel Cup engines, or engines for the Indy 500, you might want to think about buying a bolt stretch gauge.
Measuring bolt stretch tells the truth, the whole truth, and nothing but the truth.
TECH Resident
Joined: Jan 2003
Posts: 855
Likes: 0
From: AUSTIN TX
While bolt stretch is the best and most recommended method, I worked in a machine shop and built motors for over 10 years and have never done it that way. I have also reconditioned thousands of sets of rods, most with stock bolts (we were a production shop for the most part) but over a 100 sets with aftermarket bolts and even a couple sets of Carrillos And all were done using a torque wrench. That said, If i had a stretch gauge i would use it, but for now I'll just use my wrench.
All good to know. I'm looking to probably make HP somewhere in the 700 to 750 range. I'm guessing I would be ok with the torque method. At the rate I am going, I may have all winter to consider what to do.
A rod bolt stretch gauge is only like $100 from Jegs. Buy it, use it, and sleep better knowing that you did it right.
Both methods are acceptable, but like you asked, measuring stretch is better. It's like measuring bearing clearances, you can use plastiguage, but using micrometers and dial bore guages are better and more accurate. It's up to you, whatever you're comfortable with.
Both methods are acceptable, but like you asked, measuring stretch is better. It's like measuring bearing clearances, you can use plastiguage, but using micrometers and dial bore guages are better and more accurate. It's up to you, whatever you're comfortable with.
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Originally Posted by CoopDog
I have ARP rod bolts, the chrome 12 point ones. Is it better to torque them or measure for stretch? I have seen credible sources say both are acceptable. Not sure which I should go with.
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